Method and arrangement in a communications network

ABSTRACT

A method for enhancing Random Access Channel (RACH) performance is provided. First timing settings to be used by a first set of user equipments for a first Acquisition Indicator Channel (AICH) response timing are explicitly or implicitly signaled from a NodeB or from a Radio Network Controller (RNC) to a user equipment. Further, second timing settings to be used by a second set of user equipments for a second AICH response timing are explicitly or implicitly signaled from the NodeB or from the RNC to the user equipment.

RELATED APPLICATIONS

This application is a continuation of prior U.S. application Ser. No.13/262,579, filed Sep. 30, 2011, which was the National Stage ofInternational Application No. PCT/SE2011/051119, filed Sep. 19, 2011,which claims the benefit of U.S. Provisional Application No. 61/407,942filed Oct. 29, 2010, the disclosures of each of which are incorporatedherein by reference in their entirety.

TECHNICAL FIELD

Embodiments herein relate to a user equipment, a method therein, aNodeB, and a method in a network. In particular, it relates to enhancingRandom Access Channel (RACH) performance.

BACKGROUND

Communication devices such as User Equipments (UE) are also known ase.g., mobile terminals, wireless terminals and/or mobile stations. Userequipments are enabled to communicate wirelessly in a cellularcommunications network or wireless communication system, sometimes alsoreferred to as a cellular radio system or cellular networks. Thecommunication may be performed e.g., between two user equipments,between a user equipment and a regular telephone and/or between a userequipment and a server via a Radio Access Network (RAN) and possibly oneor more core networks, comprised within the cellular communicationsnetwork.

User equipments may further be referred to as mobile telephones,cellular telephones, or laptops with wireless capability, just tomention some further examples. The user equipments in the presentcontext may be, for example, portable, pocket-storable, hand-held,computer-comprised, or vehicle-mounted mobile devices, enabled tocommunicate voice and/or data, via the RAN, with another entity, such asanother user equipment or a server.

The cellular communications network covers a geographical area which isdivided into cell areas, wherein each cell area being served by a basestation, e.g., a Radio Base Station (RBS), which sometimes may bereferred to as e.g., “eNB”, “NodeB”, “NodeB”, “B node”, or BTS (BaseTransceiver Station), depending on the technology and terminology used.The base stations may be of different classes such as e.g., macro NodeB,home NodeB or pico base station, based on transmission power and therebyalso cell size. A cell is the geographical area where radio coverage isprovided by the base station at a base station site. One base station,situated on the base station site, may serve one or several cells.Further, each base station may support one or several communicationtechnologies. The base stations communicate over the air interfaceoperating on radio frequencies with the user equipments within range ofthe base stations.

In some RANs, several base stations may be connected, e.g., by landlinesor microwave, to a radio network controller, e.g., a Radio NetworkController (RNC) in Universal Mobile Telecommunications System (UMTS),and/or to each other. The radio network controller, also sometimestermed a Base Station Controller (BSC) e.g., in GSM, may supervise andcoordinate various activities of the plural base stations connectedthereto. GSM is an abbreviation for Global System for MobileCommunications (originally: Groupe Spécial Mobile).

In 3rd Generation Partnership Project (3GPP) Long Term Evolution (LTE),base stations, which may be referred to as eNodeBs or even eNBs, may bedirectly connected to one or more core networks.

UMTS is a third generation mobile communication system, which evolvedfrom the GSM, and is intended to provide improved mobile communicationservices based on Wideband Code Division Multiple Access (WCDMA) accesstechnology. UMTS Terrestrial Radio Access Network (UTRAN) is essentiallya radio access network using wideband code division multiple access foruser equipments. The 3GPP has undertaken to evolve further the UTRAN andGSM based radio access network technologies.

According to 3GPP/GERAN, a user equipment has a multi-slot class, whichdetermines the maximum transfer rate in the uplink and downlinkdirection. GERAN is an abbreviation for GSM EDGE Radio Access Network.EDGE is further an abbreviation for Enhanced Data rates for GSMEvolution.

In the context of this disclosure, the expression Downlink (DL) is usedfor the transmission path from the base station to the mobile station.The expression Uplink (UL) is used for the transmission path in theopposite direction i.e., from the mobile station to the base station.

RACH is a common uplink transport channel used by a user equipment toaccess a network in case the user equipment does not have a dedicateduplink. The RACH channel may be used for transmitting data in Cell_FACHstate. The RACH channel is often carrying signaling e.g., buffer-statusmeasurements, cell update messages, etc., that will trigger a statechange from Cell_FACH state to Cell_DCH state, where a dedicated uplinkchannel is available.

The CELL_DCH state is e.g., characterized by:

A dedicated physical channel is allocated to the user equipment inuplink and downlink.

The user equipment is known on cell level according to its currentactive set.

Downlink and uplink dedicated transport channels, downlink sharedtransport channels, and a combination of these transport channels can beused by the user equipment.

The CELL_FACH state is e.g., characterized by:

No dedicated physical channel is allocated to the user equipment.

The user equipment monitors the downlink for transmissions.

The user equipment is assigned a default common or shared transportchannel in the uplink, Random Access Channel (RACH) or Common EnhancedDedicated channel (E-DCH), that it may use anytime according to theaccess procedure for that transport channel.

The position of the user equipment is known by UTRAN on cell levelaccording to the cell where the user equipment last made a cell update.

The RACH procedure comprises a power-ramping phase on the PhysicalRandom Access Channel (PRACH), where the desire is to find the correctpower level to be used by the user equipment for uplink transmission.Once a user equipment is detected on PRACH, the NodeB responds with anacquisition indication on the Acquisition Indication Channel (AICH),which acknowledges the correct power level on PRACH. The user equipmentthen continues by transmitting in-band RACH payload carried on PRACH.

In WCDMA the random access channel is divided in time into 750 accessslots per second, and there are up to 16 different preambles that can beused per scrambling code. When making a random access attempt the userequipment chooses from a subset of the access slots and selects randomlyone preamble out of a subset of the up to 16 possible preambles. Afterthe preamble has been transmitted the user equipment waits for aresponse on the acquisition indicator channel (AICH). The timing of thisresponse is determined by the parameter τ_(p-a).

If no acknowledgement is received the random access attempt continuesand a new preamble, randomly chosen from the available ones, istransmitted with higher power. This procedure is repeated until aresponse in the form of an acknowledgement or a non-acknowledgement isreceived, too many unsuccessful preamble transmissions have been made orthe maximum allowed transmit power has been used by the user equipmentfor a number of transmissions. If the user equipment is not acknowledgedduring its random access attempt it will start another random accessattempt at a later time.

The stepwise preamble power increase is called power ramping. The ideais that random access user equipments should start their transmissionswith low power to minimize the interference they generate, and with eachnew preamble that is transmitted increase the transmission power untilit is high enough for successful reception by the NodeB. When the userequipment receives an acknowledgement it stops the power ramping andtransmits the random access message with a power related to the one usedfor the last preamble.

An enhanced random access method known as “Enhanced Uplink in CELL_FACHstate” was introduced in Release 8. The releases mentioned in thisdocument relates to releases of HSPA 3GPP specifications. A portion ofthe preamble signatures may be set aside for Release 99 method andanother portion for the Release 8 method. The preamble ramping procedureis essentially the same for both methods, except that an optionalextended acquisition indication called Extended Acquisition Indication(EAI) has been introduced beside the ordinary AI. The message parts aremore different for the two methods, showing similar differences asRelease 99 Dedicated Channel (DCH) and Release 6 Enhanced DedicatedChannel (E-DCH) in the CELL_DCH state.

The problem with the existing solution is that different random accessattempts might require different levels of receiver processing to bedetected. Some preambles may be quickly detected and should then also beacknowledged quickly to keep latency down, while other preambles mightrequire more advanced processing that requires longer processing time toenable successful detection.

SUMMARY

One or more embodiments of the present disclosure provide a way ofenhancing RACH performance.

According to one or more embodiments, in a method for enhancing RandomAccess Channel (RACH) performance, first timing settings to be used by afirst set of user equipments for a first Acquisition Indicator Channel(AICH) response timing are explicitly or implicitly signaled from aNodeB or from a Radio Network Controller (RNC) to a user equipment.Further, second timing settings to be used by a second set of userequipments for a second AICH response timing are explicitly orimplicitly signaled from the NodeB or from the RNC to the userequipment.

According to one or more embodiments, in a method in a user equipmentfor enhancing Random Access Channel (RACH) performance, the userequipment receives first timing settings explicitly or implicitlysignaled from a NodeB or from a Radio Network Controller (RNC). Thefirst timing settings are to be used by a first set of user equipmentsfor a first Acquisition Indication Channel (AICH) response timing. Theuser equipment further receives second timing settings explicitly orimplicitly signaled from the NodeB or from the RNC. The second timingsettings are to be used by a second set of user equipments for AICHresponse timing. The user equipment is comprised in the second set ofuser equipments.

According to one or more embodiments, a NodeB for enhancing RandomAccess Channel (RACH) performance comprises a transmitting unitconfigured to explicitly or implicitly signal to a user equipment, firsttiming settings. The first timing settings are to be used by a first setof user equipments for a first Acquisition Indicator Channel (AICH)response timing. The transmitting unit further is configured toexplicitly or implicitly signal to the user equipment, second timingsettings to be used by a second set of user equipments for a second AICHresponse timing.

According to one or more embodiments, a user equipment for enhancingRandom Access Channel (RACH) performance comprises a receiving unitconfigured to receive first timing settings explicitly or implicitlysignaled from a NodeB or from a Radio Network Controller (RNC). Thefirst timing settings are to be used by a first set of user equipmentsfor a first Acquisition Indication Channel (AICH) response timing. Thereceiving unit is further configured to receive second timing settingsexplicitly or implicitly signaled from the NodeB or from the RNC. Thesecond timing settings are to be used by a second set of user equipmentsfor AICH response timing. The user equipment is comprised in the secondset of user equipments.

Since embodiments herein enable different processing time andconsequently different detection response times for different userequipments and/or random access attempts, user equipments with good RACHcoverage benefits from shorter acknowledgement timing which reducesdelay and latency, while at the same time user equipments with worsecoverage can benefit from more advanced RACH receivers that require moreprocessing time. This in turn results in that the RACH performance isenhanced.

An advantage of embodiments herein is that a new AICH response timingmay be used for new user equipments simultaneously with the currentlyspecified timing for legacy user equipments.

Of course, the present disclosure is not limited to the above featuresand advantages. Indeed, those skilled in the art will recognizeadditional features and advantages upon reading the following detaileddescription, and upon viewing the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic block diagram illustrating embodiments of anetwork.

FIG. 2 is a flowchart depicting embodiments of a method.

FIG. 3 is a schematic block diagram illustrating embodiments of a NodeB.

FIG. 4 is a flowchart depicting embodiments of a method in a userequipment.

FIG. 5 is a schematic block diagram illustrating embodiments of a userequipment.

FIG. 6 is a schematic block diagram illustrating random accessprocedure.

FIG. 7 is a schematic block diagram illustrating random accessprocedure.

DETAILED DESCRIPTION

Embodiments will be exemplified in the following non-limitingdescription.

Embodiments herein relate to the Random Access Procedure in UTRAN andrelates to higher layer signaling facilitating reduction of interferenceduring a preamble ramping procedure, i.e., preamble power ramping.Embodiments herein enable different processing time and consequentlydifferent detection response times for different user equipments and/orrandom access attempts. This results in that user equipments with goodRACH coverage may benefit from shorter acknowledgement timing whichreduces delay and latency, while at the same time user equipments withworse coverage may benefit from more advanced RACH receivers thatrequire more processing time.

FIG. 1 depicts a network 100, such as a wireless communications networkin which embodiments herein may be implemented. The network 100 is acellular communication network such as UTRAN comprising UMTS TerrestrialRadio Access (UTRA) and/or UMTS and/or WCDMA networks.

The network 100 comprises a NodeB. The NodeB is a radio base stationserving a cell. The NodeB is capable to serve user equipments in thecell. The user equipments may also be referred to as users. Forconvenience user equipments are often divided into two sets in thedescription below. However, user equipments may also be divided intothree or more sets and the same methods may be used also in these cases.The user equipments may e.g., be divided into different sets of userequipments with different acknowledgement timing constraints. In oneembodiment this division is based on a user equipment category or a userequipment capability.

A user equipment is located within the cell. The user equipment is insome figures is referred to as user equipment, and is configured tocommunicate within the network via the NodeB over a radio link when theuser equipment is present in the cell served by the NodeB.

The user equipment may e.g., be a mobile terminal or a wirelessterminal, a mobile phone, a computer such as e.g., a laptop, a PersonalDigital Assistant (PDA) or a tablet computer, sometimes referred to as asurf plate, with wireless capability, or any other radio network unitcapable to communicate over a radio link in a cellular communicationssystem.

The network 100 further comprises a Radio Network Controller (RNC) 130,which RNC 130 among other things has the role of configuring the cell(s)of the NodeB with cell information such as the “AICH transmissiontiming”, or “AICH response timing” using the terminology in thisdocument, and to receive uplink data transmissions from the userequipment, via NodeB, and transmit downlink data transmissions to theuser equipment, via NodeB. The RNC 130 uses the Radio Resource Control(RRC) protocol to configure the user equipment and the Node BApplication Part (NBAP) and/or Radio Network Subsystem Application Part(RNSAP) protocols to configure the NodeB.

Embodiments will firstly be described in a perspective seen from thenetwork, such as the NodeB and the RNC 130.

Embodiments of a method for enhancing RACH performance, will now bedescribed with reference to the flowchart depicted in FIG. 2. Userequipments within the network 100 are divided into one or more set ofuser equipments. In the embodiments in this example they are dividedinto two sets, a first set of user equipments and a second set of userequipments. The user equipments may be divided into the first set ofuser equipments and the second set of user equipments based on a userequipment category or a user equipment capability, such as e.g., if theysupport the extended timing or not, or if the user equipment isassociated with a release of HSPA 3GPP specification that supports theextended timing or not.

User equipment categories may e.g., relate to maximum uplink or downlinkdata rates. The user equipment may signal its category and capabilitiesto the RNC 130.

For example, many features in release 99 of HSPA 3GPP specification aremandatory, meaning that any release 99 or later user equipment supportthem. However, most newer features in later releases of the standard arenot mandatory but optional, and a user equipment's support of such anoptional feature is referred to as a user equipment capability.

For example, a possible AICH Transmission Timing settings in of HSPA3GPP specification, e.g., ‘0’ and ‘1’, are mandatory to support for allrelease 99 user equipments, and also for all newer user equipments. Butif new settings are introduced in for example in release 11, e.g., ‘2’and ‘3’ as a part of some new optional release 11 feature, then only asubset of the release 11 user equipments can be expected to implementthis particular optional R11 feature. So a release 11 user equipmentwill only use new release 11 settings if the following conditions aremet, otherwise it shall use the same settings as release 99 userequipments.

1) The user equipment has support for the optional feature.

2) The network supports the optional feature and is indicating, e.g.,via a broadcasted signal from the NodeB in the cell, that the new timingsetting should be used in the cell for user equipments that support it.

The method comprises the following actions, which actions may as well becarried out in another suitable order than described below.

Action 201

The user equipments within the network 100 are informed of which userequipments shall use which of the different processing times in action201 and 202. Each group of user equipments is informed of what timing touse, they may however not aware what timing the other user equipmentsare supposed to use.

First timing settings to be used by the first set of user equipments fora first AICH response timing are explicitly or implicitly signaled fromthe NodeB or from the RNC to the user equipment. E.g., as per Release,each cell broadcasts via its serving NodeB the “AICH transmissiontiming” that it has been configured by the RNC to use. Release and lateruser equipments will all apply this AICH transmission timing, 0 or 1,when trying to access the cell.

In some embodiments the first AICH response timing is associated with afirst level of receiver processing. E.g., in this example the firstlevel is a level that relates to a less advanced receiver processingwhich is not so time consuming.

Action 202

Second timing settings to be used by the second set of user equipmentsfor a second AICH response timing are explicitly or implicitly signaledfrom the NodeB or from the RNC 130, to the user equipment. The secondAICH response timing may be associated with a second level of receiverprocessing. This action is performed in a similar way as the signalingof the first AICH response timing action 201. E.g., in this example thesecond level is a level that relates to an advanced receiver processingwhich is more time consuming than the first level. In these embodiments,the second set of user equipments may refer to newer user equipments oflater releases compared to the first set of user equipments.

In some embodiments the first timing settings is used also by the secondset of user equipments. The idea here is that a user equipment thatbelongs to the second set of user equipments, i.e., a newer userequipment will first try the first/older timing and if it doesn'treceive an AICH response at this setting, it will wait a little longerand see if there is an AICH response at the second/newer timing.

The second AICH response timing may for example be extended compared tothe first AICH response timing, or vice versa.

In this example the user equipment is comprised in the second set, butit may also be comprised in the first set.

Action 203

As mentioned above, the RACH procedure comprises a power-ramping phaseon the PRACH, where the desire is to find the correct power level. Oncea user equipment is detected on PRACH, the Node B responds with anacquisition indication on the AICH, which acknowledges the correct powerlevel for the user equipment to use for uplink transmission on PRACH.The user equipment then continues by transmitting RACH payload carriedon PRACH. This will be further described below with reference to FIGS. 6and 7. The user equipment starts the RACH procedure by transmitting aPRACH preamble to the NodeB.

In this action, the NodeB detects the PRACH preamble associated with theuser equipment, using the second level of receiver processing. In thisexample, the NodeB may use its more advanced RACH receiver that requiremore processing time, since the user equipment being comprised in thesecond set of user equipments is informed of the second AICH responsetiming to be used, which second AICH response timing in this example isextended, compared to the first AICH response timing. For example, whenthe more generous AICH response timing is used, the NodeB has sufficienttime to cancel the interference from other user equipments such as inthe form of E-DCH transmissions, before the NodeB has to try to detectthe PRACH preamble and send the corresponding AICH response.

Action 204

When the PRACH preamble is detected, the NodeB transmits an acquisitionindication to the user equipment. This is performed according to thesecond AICH response timing. The user equipment has been informed aboutthe second AICH response timing and is therefore aware of when theacquisition indication may be expected.

To perform the method actions described above for enhancing RACHperformance, the NodeB comprises the following arrangement depicted inFIG. 3. As mentioned above, user equipments within the network aredivided into two or more set of user equipments. The embodiments in thisexample they are divided into two sets, a first set of user equipmentsand a second set of user equipments. The user equipments may be dividedinto the first set of user equipments and the second set of userequipments based on a user equipment category or a user equipmentcapability.

The NodeB comprises a transmitting unit configured to explicitly orimplicitly signal to the user equipment, first timing settings to beused by a first set of user equipments for a first AICH response timing.

The transmitting unit is further configured to explicitly or implicitlysignal to the user equipment, second timing settings to be used by asecond set of user equipments for a second AICH response timing. Theuser equipment is comprised in the second set. In some embodiments thefirst AICH response timing is associated with a first level of receiverprocessing, and the second AICH response timing is associated with asecond level of receiver processing. The second AICH response timing mayfor example be extended compared to the first AICH response timing.

The transmitting unit 310 may further be configured to transmit anacquisition indication to the user equipment according to the secondAICH response timing and also according to the first AICH responsetiming.

In some embodiments, the first timing settings are used also by thesecond set of user equipments.

The NodeB further comprises a receiving unit configured to detect aPhysical RACH preamble associated with the user equipment, using thesecond level of receiver processing.

The embodiments herein for enhancing RACH performance may be implementedthrough one or more processors, such as a processor in the NodeBdepicted in FIG. 3, together with computer program code for performingthe functions and actions of the embodiments herein. The program codementioned above may also be provided as a computer program product, forinstance in the form of a data carrier carrying computer program codefor performing the embodiments herein when being loaded into the NodeB.One such carrier may be in the form of a CD ROM disc. It is howeverfeasible with other data carriers such as a memory stick. The computerprogram code may furthermore be provided as program code on a server anddownloaded to the NodeB.

The NodeB may further comprise a memory comprising one or more memoryunits. The memory 340 is arranged to be used to store data such aspreambles, timing settings such as the first and second timing settings,schedulings, and applications to perform the methods herein when beingexecuted in the NodeB.

Below, embodiments will be described in a perspective seen from the userequipment. Embodiments of a method in the user equipment for enhancingRACH performance will now be described with reference to the flowchartdepicted in FIG. 4. User equipments within the network 100 are dividedinto two or more set of user equipments. In the embodiments in thisexample they are divided into two sets, a first set of user equipmentsand a second set of user equipments. In some embodiments, the userequipments are divided into the first set of user equipments and thesecond set of user equipments based on a user equipment category or auser equipment capability. The division into the first and second set ofuser equipment will be further described below.

The method comprises the following actions, which actions may as well becarried out in another suitable order than described below.

Action 401

The user equipment receives first timing settings explicitly orimplicitly signaled from the NodeB or from the RNC 130. The first timingsettings are to be used by the first set of user equipments for a firstAICH, response timing.

In some embodiments, the first AICH response timing is associated with afirst level of receiver processing.

Action 402

The user equipment further receives second timing settings explicitly orimplicitly signaled from the NodeB or from the RNC 130. The secondtiming settings are to be used by the second set of user equipments forAICH response timing. The user equipment is comprised in the second setof user equipments. In some embodiments, the second AICH response timingis associated with a second level of receiver processing within theNodeB. The second AICH response timing may be extended compared to thefirst AICH response timing. E.g., in this example the second level is alevel that relates to an advanced receiver processing which is more timeconsuming than the first level. In these embodiments, the second set ofuser equipments may refer to newer user equipments of later releasescompared to the first set of user equipments.

The first timing settings may be used also by the user equipmentcomprised in the second set of user equipments. As mentioned above, theidea here is that the user equipment that belongs to the second set ofuser equipments, i.e., a newer user equipment will first try the firsttiming and if it does not receive an AICH response at this setting, itwill wait a little longer and see if there is an AICH response at thesecond timing.

In some embodiments, the user equipment also uses multiple AICH responsetimings.

Action 403

The user equipment starts a RACH procedure by transmitting a PRACHpreamble to the NodeB.

Action 404

In this example, the NodeB may use its advanced RACH receiver thatrequire more processing time, since the user equipment being comprisedin the second set of user equipments is informed of the second AICHresponse timing to be used, that in this example is extended compared tothe first AICH response timing. When the PRACH preamble is detected bythe NodeB, NodeB transmits an acquisition indication. So in this action404, the user equipment receives the acquisition indication from theNodeB according to the second timing settings. The user equipment hasbeen informed about the second AICH response timing and is thereforeaware of when the acquisition indication may be expected.

In some embodiments the user equipment waits for a first response in anAICH access slot according to the shortest AICH response timingrequirements when having transmitted a Physical RACH preamble to theNodeB. If no response is received the user equipment checks for aresponse regarding the same Physical RACH preamble transmission in alater AICH access slot according to the second shortest AICH responsetiming requirement.

To perform the method actions described above for enhancing RACHperformance, the user equipment comprises the following arrangementdepicted in FIG. 5. As mentioned above, user equipments within thenetwork 100 are divided into one or more set of user equipments. In theembodiments in this example they are divided into two sets, a first setof user equipments and a second set of user equipments. The userequipments may for example be divided into the first set of userequipments and the second set of user equipments based on a userequipment category or a user equipment capability.

The user equipment comprises a receiving unit 510 configured to receivefirst timing settings explicitly or implicitly signaled from the NodeBor from the RNC 130. The first timing settings are to be used by thefirst set of user equipments for a first AICH response timing, whichfirst AICH response timing is associated with a first level of receiverprocessing.

The receiving unit 510 is further configured to receive second timingsettings explicitly or implicitly signaled from the NodeB or from theRNC 130. The second timing settings are to be used by a second set ofuser equipments for AICH response timing. The user equipment iscomprised in the second set of user equipments.

The second AICH response timing may be extended compared to the firstAICH response timing. In some embodiments, the first AICH responsetiming is associated with a first level of receiver processing withinthe NodeB, and the second AICH response timing is associated with asecond level of receiver processing within the NodeB. The first timingsettings may be used also by the user equipment comprised in the secondset of user equipments.

The receiving unit 510 may further be configured to receive anacquisition indication from the NodeB according to the second timingsettings. The user equipment may in some embodiments use multiple AICHresponse timings.

The receiving unit 510 may further be configured to wait for a firstresponse in an AICH access slot according to the shortest AICH responsetiming requirements when having transmitted a Physical RACH preamble tothe NodeB, and to check for a response regarding the same Physical RACHpreamble transmission in a later AICH access slot according to thesecond shortest AICH response timing requirement if no response isreceived.

The user equipment further comprises a transmitting unit configured totransmit a Physical RACH preamble to the NodeB.

The embodiments herein for enhancing RACH performance may be implementedthrough one or more processors, such as a processor in the userequipment depicted in FIG. 5, together with computer program code forperforming the functions and actions of the embodiments herein. Theprogram code mentioned above may also be provided as a computer programproduct, for instance in the form of a data carrier carrying computerprogram code for performing the embodiments herein when being loadedinto the in the user equipment. One such carrier may be in the form of aCD ROM disc. It is however feasible with other data carriers such as amemory stick. The computer program code may furthermore be provided aspure program code on a server and downloaded to the user equipment.

The user equipment may further comprise a memory comprising one or morememory units. The memory 540 is arranged to be used to store data suchas preambles, timing settings such as the first and second timingsettings, schedulings, and applications to perform the methods hereinwhen being executed in the user equipment.

Embodiments Applicable to all the Embodiments Described Above

In the following, embodiments are described which are applicable to thevariants and embodiments described above.

As mentioned above, the RACH procedure includes a power-ramping phase onthe PRACH, to find the correct power level, which may be seen in FIG. 6.FIG. 6 illustrates random access behavior. The upper axis depicts DLAICH access slots, and the lower axis depicts UL PRACH access slots seenfrom the user equipment. A power-ramping on PRACH is followed by anindication on the AICH. A positive acknowledgement on AICH will resultin a transmission of data on PRACH carrying RACH payload.

Once user equipment is detected on PRACH, the Node B 110 responds withan acquisition indication on the AICH, which acknowledges the correctpower level on PRACH. The user equipment then continues by transmittingRACH payload carried on PRACH.

As user equipments begin to spend more time in CELL_FACH instead ofCELL_DCH, the preamble detection performance becomes more important. Atthe same time, the preamble detection becomes more and more challengingdue to the desire to operate at a higher noise rise due to the increaseduplink throughput demands and uplink peak rate improvements.

Relatively minor changes to the preamble ramping procedure may beconsidered in order to help retain the uplink coverage for the preamblepart in scenarios where E-DCH is operated with a high noise rise. Oneapproach according to embodiments herein is to increase the timeprovided between the preamble detection and the required response onAICH in order to enable usage of more advanced preamble receivers suchas Interference Cancellation IC receivers. The interference may be E-DCHtransmissions from other user equipments, user equipments that mayreside in Cell_FACH or Cell_DCH state. In interference cancellation thesignals from interfering user equipments are received, regenerated andsubtracted from the received signal before the reception of the desireduser equipments signal, in this example the RACH preamble. This helpsreduce the interference when detecting the preamble part and/or reducethe latency for the message part as fewer preambles may be needed duringeach access attempt. Typically it is interference from other signalsthat are cancelled to benefit the preamble detection, so it is not theinterference from the preamble that is cancelled.

FIG. 7 depicts timing relation between PRACH and AICH as seen at theuser equipment. In WCDMA the random access channel is divided in timeinto 750 access slots per second, and there are up to 16 differentpreambles that can be used per scrambling code. When making a randomaccess attempt the user equipment chooses from a subset of the accessslots and must randomly select one preamble out of a subset of the up to16 possible preambles. After the preamble has been transmitted the userequipment waits for a response on the AICH. The timing of this responseis determined by the parameter τ_(p-a).

In embodiments related to 3GPP based systems the multiple timingsettings may be realized by using multiple, different, parametersτ_(p-a), see FIG. 7. These parameter values may be explicitly orimplicitly signaled by the network, either as broadcasted cellinformation from the Node B 110 to the user equipment or as dedicatedRRC signaling from the RNC 130 to the user equipment.

In the timing relation for Common E-DCH the values of τ_(p-p) andτ_(p-a) depend on the setting of higher layer parameterAICH_Transmisson_Timing. τ_(p-p) is the inter-preamble time periodicityfor subsequent preambles in the preamble ramping procedure. For example:

When AICH_Transmission_Timing is set to 0, then

-   -   τ_(p-p)=3 access slot    -   τ_(p-a)=1.5 access slot

When AICH_Transmission_Timing is set to 1, then

-   -   τ_(p-p)=4 access slot    -   τ_(p-a)=2.5 access slots

The time available for the NodeB processing needed for the preambledetection before the response needs to be transmitted on AICH, isdecreased by the round trip time, i.e., the propagation delay times two.

There is very limited time available for any sort of advanced processingof the signal. As mentioned above, the second AICH response timing maybe extended compared to the first AICH response timing. This may beperformed by increasing τ_(p-p) and τ_(p-a) in order to provide moretime for NodeB processing. The easiest way is to introduce additionalvalues for AICH_Transmission_Timing, for example:

When AICH_Transmission_Timing is set to 2, then

-   -   τ_(p-p)=6 access slots    -   τ_(p-a)=4.5 access slots

When AICH_Transmission_Timing is set to 3, then

-   -   τ_(p-p)=7 access slots    -   τ_(p-a)=5.5 access slots

In the above examples it is assumed that 3 additional slots are neededto wait for the 2-ms E-DCH TTI to be received and 1-3 slots for advancedprocessing (IC). This additional parameter value would only be availablefor new user equipments supporting the enhancement, such as the userequipment according to this example. The exact values may require somefurther investigation. Assuming that Rel-11 user equipments supporting“Further Enhancements to CELL_FACH” will access the network 100 using aspecific subset of the available preamble signatures, possibly on aseparate uplink scrambling code, a separate AICH_Transmission_Timingparameter may be used for these signatures. Legacy user equipments arestill supported but they will not enjoy the improved preamble detectionperformance in high noise rise scenarios. One way to handle this is tooperate different carriers with different noise rise targets.

According to some embodiments, the second set of user equipments useanother scrambling code than a scrambling code used by the first set ofuser equipments for RACH transmission, i.e., the new timingconfiguration. The user equipments scramble their preambles with ascrambling code. This scrambling code is most often the same for alluser equipments today. To make it possible for the NodeB to dividerelease 99 user equipments from user equipments that support the newextended timing AND have been configured by the network by RNC 130and/or NodeB to apply the extended timing, e.g., new release 11 userequipments or any later release user equipments, the system may tell therelease 11 or later user equipments to use a second scrambling code.Then the NodeB RACH preamble detector will know which kind of userequipment it has detected based on the scrambling code that the userequipments used. E.g., when the NodeB detects that a preamble from theuser equipment, is scrambled with the second scrambling code, the NodeBknow that it is a release 11 user equipment, that it has more time foradvanced processing and that it can transmit the detection response onAICH at a later time.

In some embodiments, different subsets of available preamble signaturesand/or different subsets of the available access slots are used toseparate the different first and second sets of user equipments withdifferent AICH response timings, i.e., acknowledgement timings. Thesystem, i.e., the network 100 broadcasts information to the userequipments not only about which scrambling code they should use whenscrambling their RACH preambles, but also about which preamblesignatures are allowed to be used by different user equipment categoriesand in what access slots different user equipment categories are allowedto transmit their RACH preambles. It is the preamble signature that isscrambled and the result is the final preamble signal. This gives anoperator the possibility to give some groups of user equipments a VeryImportant Person (VIP) status so that in certain access slots, timeperiods, only the VIP user equipments may make a random access attemptto set up a connection. This may be used for emergency calls so thatthose calls are not interfered by other random access attempts. But thismay also be used to divide the available access slots, such as timechunks, into release 99-only access slots and release 11-only accessslots so that when the NodeB RACH preamble detector hears a preamble itknows if it is from a release 99 or release 11 user equipment because itknows which access slot is currently being processed.

An EAI signature may be used as a response to a corresponding RACHpreamble signature as a one-to-one mapping for one out of: the first setof user equipments and second set of user equipments. This is anadvantage because for example when the response on AICH will come at anew, delayed, point in time for a user equipment in the second set ofuser equipments such as e.g., a release 11 user equipment, it mayinterfere and be mixed up with an AICH response that is transmitted atthe same time for a user equipment in the first set of user equipmentssuch as a release 99 user equipment, which was detected later than therelease 11 user equipment but due to the shorter response time, i.e.,the responses where transmitted simultaneously. By then instead usingEAI instead of AI as the response, the user equipments will not beconfused. The EAI and AI do not interfere with each other.

This means that the acknowledgments on AICH that are sent using thesecond timing setting was to be acknowledged with an EAI instead of anAI. This may be necessary if both first and second sets of userequipments use all available RACH signatures, then a way to distinguishbetween acknowledgements for the first and second timing settings wouldbe to use AI for the first timing setting and EAI for the second timingor vice versa. If both used AI then there may be collisions: Assume thattwo user equipments, one from the first set of user equipments and onefrom the second set of user equipments both transmit preambles, but theuser equipment from the first set of user equipments sends its preamblea bit later than the user equipment from the second set of userequipments. Then in some cases both user equipments will expect theacknowledgment in the same access slot. Then it is good to distinguishthe two acknowledgements from each other by using AI for the firsttiming and EAI for the second timing or vice versa.

As mentioned above, the first timing settings may be used also by theuser equipment comprised in the second set of user equipments. Accordingto some embodiments, if a second set user equipment can use both a firstand a second timing setting it will wait for an acknowledgement using AIafter the first time interval. If it does not receive it, second setuser equipment waits for EAI that will maybe come a bit later if theNodeB using the second level of advanced receiver processing is able todetect the preamble. E.g., an AI signature may be used as a response toa corresponding RACH preamble signature from a user equipment in thefirst set of user equipments, and an EAI, signature may be used as aresponse to a corresponding RACH preamble signature from a userequipment from the second set of user equipments.

As mentioned above, in some embodiments some user equipments use onlyone response timing while other sets of user equipments use multipletimings. An example of the latter sort of user equipment is when theuser equipment is a user equipment that transmits a preamble and waitsfor a first response in the AICH access slot according to the shortesttiming requirements, and if no response is received, it checks for aresponse regarding the same preamble transmission in a later AICH accessslot according to the second shortest timing requirement, etc.

In one embodiment the first set of user equipments use the random accessand AICH response timing, i.e., according to the second timing settings,as specified in either Release 99 or Release 8 of the 3GPPspecifications. A second set of user equipments use a new random accessand AICH response timing configuration, i.e., according to the secondtiming settings. In one embodiment these user equipments areacknowledged using the EAIs in AICH. The second set of user equipmentsmay possibly also, in addition, use the first response timing and thenbe acknowledged according to Release 8 of the 3GPP specifications.

In one embodiment as mentioned above, each EAI signature is used as aresponse to a corresponding RACH preamble signature as a one-to-onemapping for one set of user equipments.

When using the word “comprise” or “comprising” it shall be interpretedas non-limiting, i.e., meaning “consist at least of”.

The embodiments herein are not limited to the above described preferredembodiments. Various alternatives, modifications and equivalents may beused. Therefore, the above embodiments should not be taken as limitingthe scope of the disclosure, which is defined by the appending claims.

Thus, the foregoing description and the accompanying drawings representnon-limiting examples of the methods and apparatus taught herein. Assuch, the present disclosure is not limited by the foregoing descriptionand accompanying drawings. Instead, the present disclosure is limitedonly by the following claims and their legal equivalents.

What is claimed is:
 1. A method in a user equipment (UE) for enhancingRandom Access Channel (RACH) performance, comprising: receiving firsttiming settings explicitly or implicitly signaled from a NodeB or from aRadio Network Controller (RNC) to be used by a first set of UEs for afirst Acquisition Indication Channel (AICH) response timing; receivingsecond timing settings explicitly or implicitly signaled from the NodeBor from the RNC to be used by a second set of UEs for a second AICHresponse timing, wherein the UE is included in the second set of UEs;transmitting a Physical RACH preamble to the NodeB; waiting for aresponse to the Physical RACH preamble in an AICH access slot accordingto a shortest one of the first AICH response timing and the second AICHresponse timing; and if no response is received, checking for a responseregarding the same Physical RACH preamble transmission in a later AICHaccess slot according to a second shortest of the first AICH responsetiming and the second AICH response timing.
 2. The method of claim 1,wherein the first AICH response timing is associated with a first levelof receiver processing, and wherein the second AICH response timing isassociated with a second level of receiver processing within the NodeB.3. The method of claim 1, wherein the second AICH response timing isextended compared to the first AICH response timing.
 4. The method ofclaim 1, further comprising: transmitting a Physical RACH preamble tothe NodeB; receiving an acquisition indication from the NodeB accordingto the second timing settings.
 5. The method of claim 1, wherein thesecond set of UEs use a scrambling code other than a scrambling codeused by the first set of UEs for RACH transmission.
 6. The method ofclaim 1, wherein different subsets of available preamble signatures,different subsets of available access slots, or both, are used toseparate the different first and second sets of UEs with different AICHresponse timings.
 7. The method of claim 1, further comprising receivingan Extended Acquisition Indication (EAI) signature as a response to acorresponding RACH preamble signature, the EAI signature correspondingto a one-to-one mapping for one of the first set of UEs and the secondset of UEs.
 8. The method of claim 1, wherein the UE uses multiple AICHresponse timings.
 9. A user equipment (UE) for enhancing Random AccessChannel (RACH) performance, comprising: a receiving circuit configuredto: receive first timing settings explicitly or implicitly signaled froma NodeB or from a Radio Network Controller (RNC) for use by a first setof UEs for a first Acquisition Indication Channel (AICH) responsetiming; receive second timing settings explicitly or implicitly signaledfrom the NodeB or from the RNC, for use by a second set of UEs for asecond AICH response timing, and wherein the UE is included in thesecond set of UEs; wait for a first response in an AICH access slotaccording to a shortest one of the first AICH response timing and thesecond AICH response timing when the transmitting circuit hastransmitted a Physical RACH preamble to the NodeB; check for a responseregarding the same Physical RACH preamble transmission in a later AICHaccess slot according to a second shortest of the first AICH responsetiming and the second AICH response timing if no response is received.10. The UE of claim 9, wherein the first AICH response timing isassociated with a first level of NodeB receiver processing, and whereinthe second AICH response timing is associated with a second level ofNodeB receiver processing.
 11. The UE of claim 9, wherein the secondAICH response timing is extended compared to the first AICH responsetiming.
 12. The UE of claim 9: further comprising a transmitting circuitconfigured to transmit a Physical RACH preamble to the NodeB; whereinthe receiving circuit is further configured to receive an acquisitionindication from the NodeB according to the second timing settings. 13.The UE of claim 9, wherein the second set of UEs use a scrambling codeother than a scrambling code used by the first set of UEs for RACHtransmission.
 14. The UE of claim 9, wherein different subsets ofavailable preamble signatures, different subsets of available accessslots, or both, are used to separate the different first and second setsof UEs with different AICH response timings.
 15. The UE of claim 9,wherein the receiving circuit is further configured to receive anExtended Acquisition Indication (EAI) signature as a response to atransmitted RACH preamble signature, the EAI signature corresponding toa one-to-one mapping for one of the first set of UEs and the second setof UEs.
 16. The UE of claim 9, wherein the transmitting circuit isfurther configured to use multiple AICH response timings.